It is desirable to provide the features and advantages associated with stored program controlled switching to small communities. However, many small communities cannot economically justify the installation of independent, stored program-controlled systems. This situation has led to the development of systems in which a remote switching network can be controlled over a communication link by the central control of a host electronic switching system. One such system, the Western Electric No. 10A Remote Switching System (RSS) described in the Bell System Technical Journal, Vol. 61, No. 4, April 1982, can serve up to 2048 lines and has a stand-alone capability where basic service is maintained for intra-RSS calls in the event of a failure of the host system or the communication link between the host and remote units. The economic advantages involved in sharing a host system central control can also be realized by installing several remote switching systems in a larger community having more lines than can be accommodated by a single remote system. However, installing separate remote systems to serve a single community may have several disadvantages. When one of the links to the host system fails, stand-alone operation of separate remote systems may result in the isolation of highly interactive portions of the community. Further, voice and data traffic among the separate remote systems must be conveyed via the host system network. The resulting increase in traffic through the host system network increases the number of the expensive transmission facilities required to connect the host system to separate remote units and may make impractical the connection of such remote units to an available host system network which is already operating near its maximum capacity.
In view of the foregoing, a recognized problem in the art is providing remote switching service to a community having more lines than are accommodated by a single remote system while avoiding the isolation of different parts of the community during stand-alone operation and without unnecessarily routing voice and data traffic through the host system network during normal operation.